This invention relates to an axe or wedge for splitting wood.
Devices are well known for use in splitting wood, such as logs. An example of a wedge type device particularly adapted for such use is shown in U.S. Pat. No. 3,865,163, issued Feb. 11, 1975 to Charles M. Root. In the device shown in this patent, a wedge is attached to a piston rod or the like, to which a pair of lever arms are also attached. The piston rod forces the wedge into the log to be split and, upon the wedge passing into the log in a conventional way, the lever arms engage the opening in the log and force the log apart. This device uses a toggle principle for the lever arms, and the splitting force exerted by the arms is at a minimum upon the arms engaging the wood at the commencement of splitting. The splitting force gradually increases as the arms rotate toward the horizontal. However, the maximum splitting force is desirable on the initiation of splitting, rather than at completion.
An example of an axe type device for use in splitting logs is shown in U.S. Pat. No. 4,044,808, issued Aug. 30, 1977 to Robert A. Kolonia. In this device, a conventional axe head is modified by the addition of a pair of crossed lever arms which are pivotally offset with respect to each other and the central axis of the head. The lever arms are crossed so as to extend through the head transversely, each being pivoted on one side of the head and protruding from the opposite side. The axe is utilized in conventional fashion. The lever arms engage the log to be split, at the commencement of splitting, and, as the axe head enters the split, the lever arms pivot outwardly to provide an increasing splitting pressure on the log. Thus, again in the type construction, which eventually provides a greater splitting action for a given downward force, results in an increasing splitting force being applied as the levers rotate toward the horizontal. As the levers approach horizontal, little downward energy is applied by the axe head, and it may become stuck in the split. Also, in such an axe head, the lever arms become locked in an outward protruding position in the log, and so provide considerable resistance to downward pressure, if the log has not already split. Because in the locked position the lever arms are substantially normal to the direction at thrust of the axe head, a greatly increased downward thrust is necessary to accomplish further downward movement of the axe head through the wood, often, this problem requires the stuck axe head being struck with a sledge to provide further splitting. Further, because the pivot points for the lever arms are offset from the center of the head, a blow by the axe which is either not quite vertical or which strikes a knot or other discontinuity in the log, causes the axe head to lose its balance and to be diverted from its downward path with a resultant uneven splitting of the log, or even create a very dangerous side trajectory of the axe. As in U.S. Pat. No. 3,865,163, the minimum splitting force exists as the levers initially contact the wood, and the relatively flat surfaces existing at the point of impact when splitting is initially attempted result in an abrupt energy transfer from the axe to the log, often causing the axe to rebound from the wood, if hard wood or a large diameter log is attempted to be split.